Researchers Construct Carbon Nanotube Device That Can Detect Colors of the Rainbow
Researchers at Sandia National Laboratories have created the first carbon nanotube device that can detect the entire visible spectrum of light, a feat that could soon allow scientists to probe single molecule transformations, study how those molecules respond to light, observe how the molecules change shapes, and understand other fundamental interactions between molecules and nanotubes.
Carbon nanotubes are long thin cylinders composed entirely of carbon atoms. While their diameters are in the nanometer range (1-10), they can be very long, up to centimeters in length.
The carbon-carbon bond is very strong, making carbon nanotubes very robust and resistant to any kind of deformation. To construct a nanoscale color detector, Sandia researchers took inspiration from the human eye, and in a sense, improved on the model.
When light strikes the retina, it initiates a cascade of chemical and electrical impulses that ultimately trigger nerve impulses. In the nanoscale color detector, light strikes a chromophore and causes a conformational change in the molecule, which in turn causes a threshold shift on a transistor made from a single-walled carbon nanotube.
“In our eyes the neuron is in front of the retinal molecule, so the light has to transmit through the neuron to hit the molecule,” says Sandia researcher Xinjian Zhou. “We placed the nanotube transistor behind the molecule—a more efficient design.”
Zhou and his Sandia colleagues François Léonard, Andy Vance, Karen Krafcik, Tom Zifer, and Bryan Wong created the device. The team recently published a paper, “Color Detection Using Chromophore-Nanotube Hybrid Devices,” in the journal Nano Letters.
The idea of carbon nanotubes being light sensitive has been around for a long time, but earlier efforts using an individual nanotube were only able to detect light in narrow wavelength ranges at laser intensities. The Sandia team found that their nanodetector was orders of magnitude more sensitive, down to about 40 W/m2—about 3 percent of the density of sunshine reaching the ground. “Because the dye is so close to the nanotube, a little change turns into a big signal on the device,” says Zhou.
The research is in its second year of internal Sandia funding and is based on Léonard’s collaboration with the University of Wisconsin to explain the theoretical mechanism of carbon nanotube light detection. Léonard literally wrote the book on carbon nanotubes—The Physics of Carbon Nanotubes, published September 2008.
Léonard says the project draws upon Sandia’s expertise in both materials physics and materials chemistry. He and Wong laid the groundwork with their theoretical research, with Wong completing the first-principles calculations that supported the hypothesis of how the chromophores were arranged on the nanotubes and how the chromophore isomerizations affected electronic properties of the devices.
To construct the device, Zhou and Krafcik first had to create a tiny transistor made from a single carbon nanotube. They deposited carbon nanotubes on a silicon wafer and then used photolithography to define electrical patterns to make contacts.
The final piece came from Vance and Zifer, who synthesized molecules to create three types of chromophores that respond to either the red, green, or orange bands of the visible spectrum. Zhou immersed the wafer in the dye solution and waited a few minutes while the chromophores attached themselves to the nanotubes.
The team reached their goal of detecting visible light faster than they expected—they thought the entire first year of the project would be spent testing UV light. Now, they are looking to increase the efficiency by creating a device with multiple nanotubes.
“Detection is now limited to about 3 percent of sunlight, which isn’t bad compared with a commercially available digital camera,” says Zhou. “I hope to add some antennas to increase light absorption.”
A device made with multiple carbon nanotubes would be easier to construct and the resulting larger area would be more sensitive to light. A larger size is also more practical for applications.
Now, they are setting their sites on detecting infrared light. “We think this principle can be applied to infrared light and there is a lot of interest in infrared detection,” says Vance. “So we’re in the process of looking for dyes that work in infrared.”
This research eventually could be used for a number of exciting applications, such as an optical detector with nanometer scale resolution, ultra-tiny digital cameras, solar cells with more light absorption capability, or even genome sequencing. The near-term purpose, however, is basic science.
“A large part of why we are doing this is not to invent a photo detector, but to understand the processes involved in controlling carbon nanotube devices,” says Léonard.
The next step in the project is to create a nanometer-scale photovoltaic device. Such a device on a larger scale could be used as an unpowered photo detector or for solar energy. “Instead of monitoring current changes, we’d actually generate current,” says Vance. “We have an idea of how to do it, but it will be a more challenging fabrication process.”
--------------------------------------------------------------------------------
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif.Researchers at Sandia National Laboratories have created the first carbon nanotube device that can detect the entire visible spectrum of light, a feat that could soon allow scientists to probe single molecule transformations, study how those molecules respond to light, observe how the molecules change shapes, and understand other fundamental interactions between molecules and nanotubes.
Carbon nanotubes are long thin cylinders composed entirely of carbon atoms. While their diameters are in the nanometer range (1-10), they can be very long, up to centimeters in length.
The carbon-carbon bond is very strong, making carbon nanotubes very robust and resistant to any kind of deformation. To construct a nanoscale color detector, Sandia researchers took inspiration from the human eye, and in a sense, improved on the model.
When light strikes the retina, it initiates a cascade of chemical and electrical impulses that ultimately trigger nerve impulses. In the nanoscale color detector, light strikes a chromophore and causes a conformational change in the molecule, which in turn causes a threshold shift on a transistor made from a single-walled carbon nanotube.
“In our eyes the neuron is in front of the retinal molecule, so the light has to transmit through the neuron to hit the molecule,” says Sandia researcher Xinjian Zhou. “We placed the nanotube transistor behind the molecule—a more efficient design.”
Zhou and his Sandia colleagues François Léonard, Andy Vance, Karen Krafcik, Tom Zifer, and Bryan Wong created the device. The team recently published a paper, “Color Detection Using Chromophore-Nanotube Hybrid Devices,” in the journal Nano Letters.
The idea of carbon nanotubes being light sensitive has been around for a long time, but earlier efforts using an individual nanotube were only able to detect light in narrow wavelength ranges at laser intensities. The Sandia team found that their nanodetector was orders of magnitude more sensitive, down to about 40 W/m2—about 3 percent of the density of sunshine reaching the ground. “Because the dye is so close to the nanotube, a little change turns into a big signal on the device,” says Zhou.
The research is in its second year of internal Sandia funding and is based on Léonard’s collaboration with the University of Wisconsin to explain the theoretical mechanism of carbon nanotube light detection. Léonard literally wrote the book on carbon nanotubes—The Physics of Carbon Nanotubes, published September 2008.
Léonard says the project draws upon Sandia’s expertise in both materials physics and materials chemistry. He and Wong laid the groundwork with their theoretical research, with Wong completing the first-principles calculations that supported the hypothesis of how the chromophores were arranged on the nanotubes and how the chromophore isomerizations affected electronic properties of the devices.
To construct the device, Zhou and Krafcik first had to create a tiny transistor made from a single carbon nanotube. They deposited carbon nanotubes on a silicon wafer and then used photolithography to define electrical patterns to make contacts.
The final piece came from Vance and Zifer, who synthesized molecules to create three types of chromophores that respond to either the red, green, or orange bands of the visible spectrum. Zhou immersed the wafer in the dye solution and waited a few minutes while the chromophores attached themselves to the nanotubes.
The team reached their goal of detecting visible light faster than they expected—they thought the entire first year of the project would be spent testing UV light. Now, they are looking to increase the efficiency by creating a device with multiple nanotubes.
“Detection is now limited to about 3 percent of sunlight, which isn’t bad compared with a commercially available digital camera,” says Zhou. “I hope to add some antennas to increase light absorption.”
A device made with multiple carbon nanotubes would be easier to construct and the resulting larger area would be more sensitive to light. A larger size is also more practical for applications.
Now, they are setting their sites on detecting infrared light. “We think this principle can be applied to infrared light and there is a lot of interest in infrared detection,” says Vance. “So we’re in the process of looking for dyes that work in infrared.”
This research eventually could be used for a number of exciting applications, such as an optical detector with nanometer scale resolution, ultra-tiny digital cameras, solar cells with more light absorption capability, or even genome sequencing. The near-term purpose, however, is basic science.
“A large part of why we are doing this is not to invent a photo detector, but to understand the processes involved in controlling carbon nanotube devices,” says Léonard.
The next step in the project is to create a nanometer-scale photovoltaic device. Such a device on a larger scale could be used as an unpowered photo detector or for solar energy. “Instead of monitoring current changes, we’d actually generate current,” says Vance. “We have an idea of how to do it, but it will be a more challenging fabrication process.”
--------------------------------------------------------------------------------
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif.
Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
Showing posts with label Nanotechnology. Show all posts
Showing posts with label Nanotechnology. Show all posts
Saturday, May 02, 2009
Saturday, March 21, 2009
New Systems for Storing Electrical Energy
In order to save money and energy, many people are purchasing hybrid electric cars or installing solar panels on the roofs of their homes. But both have a problem -- the technology to store the electrical power and energy is inadequate.
Battery systems that fit in cars don't hold enough energy for driving distances, yet take hours to recharge and don't give much power for acceleration. Renewable sources like solar and wind deliver significant power only part time, but devices to store their energy are expensive and too inefficient to deliver enough power for surge demand.
Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available. The results of their research are available in the latest issue of Nature Nanotechnology.
"Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded," said Gary Rubloff, director of the University of Maryland's NanoCenter. "Conventional devices to store and deliver electrical energy -- batteries and capacitors -- cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future."
Researchers working with Professor Rubloff and his collaborator, Professor Sang Bok Lee, have developed a method to significantly enhance the performance of electrical energy storage devices.
Using new processes central to nanotechnology, they create millions of identical nanostructures with shapes tailored to transport energy as electrons rapidly to and from very large surface areas where they are stored. Materials behave according to physical laws of nature. The Maryland researchers exploit unusual combinations of these behaviors (called self-assembly, self-limiting reaction, and self-alignment) to construct millions -- and ultimately billions -- of tiny, virtually identical nanostructures to receive, store, and deliver electrical energy.
"These devices exploit unique combinations of materials, processes, and structures to optimize both energy and power density -- combinations that, taken together, have real promise for building a viable next-generation technology, and around it, a vital new sector of the tech economy," Rubloff said.
"The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power)," he continued.
Electrical energy storage devices fall into three categories. Batteries, particularly lithium ion, store large amounts of energy but cannot provide high power or fast recharge. Electrochemical capacitors (ECCs), also relying on electrochemical phenomena, offer higher power at the price of relatively lower energy density. In contrast, electrostatic capacitors (ESCs) operate by purely physical means, storing charge on the surfaces of two conductors. This makes them capable of high power and fast recharge, but at the price of lower energy density.
The Maryland research team's new devices are electrostatic nanocapacitors which dramatically increase energy storage density of such devices - by a factor of 10 over that of commercially available devices - without sacrificing the high power they traditionally characteristically offer. This advance brings electrostatic devices to a performance level competitive with electrochemical capacitors and introduces a new player into the field of candidates for next-generation electrical energy storage.
Where will these new nanodevices appear? Lee and Rubloff emphasize that they are developing the technology for mass production as layers of devices that could look like thin panels, similar to solar panels or the flat panel displays we see everywhere, manufactured at low cost. Multiple energy storage panels would be stacked together inside a car battery system or solar panel. In the longer run, they foresee the same nanotechnologies providing new energy capture technology (solar, thermoelectric) that could be fully integrated with storage devices in manufacturing.
This advance follows soon after another accomplishment, the dramatic improvement in performance (energy and power) of electrochemical capacitors (ECC's), thus 'supercapacitors,' by Lee's research group, published recently in the Journal of the American Chemical Society. (Figure 1). Efforts are under way to achieve comparable advances in energy density of lithium (Li) ion batteries but with much higher power density.
"The University of Maryland's successes are built upon the convergence and collaboration of experts from a wide range of nanoscale science and technology areas with researchers already in the center of energy research," Rubloff said.
The Research Team
Gary Rubloff is Minta Martin Professor of Engineering in the materials science and engineering department and the Institute for Systems Research at the University of Maryland's A. James Clark School of Engineering. Sang Bok Lee is associate professor in the Department of Chemistry and Biochemistry at the College of Chemical and Life Sciences and WCU (World Class University Program) professor at KAIST (Korea Advanced Institute of Science and Technology) in Korea. Lee and Rubloff are part of a larger team developing nanotechnology solutions for energy capture, generation, and storage at Maryland. Their collaborators on electrical energy storage include Maryland professors Michael Fuhrer (physics), associate director of the Maryland Nanocenter Reza Ghodssi (electrical and computer engineering), John Cumings (materials science engineering), Ray Adomaitis (chemical and biomolecular engineering), Oded Rabin (materials science and engineering), Janice Reutt-Robey (chemistry), Robert Walker (chemistry), Chunsheng Wang (chemical and biomolecular engineering), Yu-Huang Wang (chemistry) and Ellen Williams (physics), director of the Materials Research Science and Engineering Center at the University of Maryland.
In order to save money and energy, many people are purchasing hybrid electric cars or installing solar panels on the roofs of their homes. But both have a problem -- the technology to store the electrical power and energy is inadequate.Battery systems that fit in cars don't hold enough energy for driving distances, yet take hours to recharge and don't give much power for acceleration. Renewable sources like solar and wind deliver significant power only part time, but devices to store their energy are expensive and too inefficient to deliver enough power for surge demand.
Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available. The results of their research are available in the latest issue of Nature Nanotechnology.
"Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded," said Gary Rubloff, director of the University of Maryland's NanoCenter. "Conventional devices to store and deliver electrical energy -- batteries and capacitors -- cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future."
Researchers working with Professor Rubloff and his collaborator, Professor Sang Bok Lee, have developed a method to significantly enhance the performance of electrical energy storage devices.
Using new processes central to nanotechnology, they create millions of identical nanostructures with shapes tailored to transport energy as electrons rapidly to and from very large surface areas where they are stored. Materials behave according to physical laws of nature. The Maryland researchers exploit unusual combinations of these behaviors (called self-assembly, self-limiting reaction, and self-alignment) to construct millions -- and ultimately billions -- of tiny, virtually identical nanostructures to receive, store, and deliver electrical energy.
"These devices exploit unique combinations of materials, processes, and structures to optimize both energy and power density -- combinations that, taken together, have real promise for building a viable next-generation technology, and around it, a vital new sector of the tech economy," Rubloff said.
"The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power)," he continued.
Electrical energy storage devices fall into three categories. Batteries, particularly lithium ion, store large amounts of energy but cannot provide high power or fast recharge. Electrochemical capacitors (ECCs), also relying on electrochemical phenomena, offer higher power at the price of relatively lower energy density. In contrast, electrostatic capacitors (ESCs) operate by purely physical means, storing charge on the surfaces of two conductors. This makes them capable of high power and fast recharge, but at the price of lower energy density.
The Maryland research team's new devices are electrostatic nanocapacitors which dramatically increase energy storage density of such devices - by a factor of 10 over that of commercially available devices - without sacrificing the high power they traditionally characteristically offer. This advance brings electrostatic devices to a performance level competitive with electrochemical capacitors and introduces a new player into the field of candidates for next-generation electrical energy storage.
Where will these new nanodevices appear? Lee and Rubloff emphasize that they are developing the technology for mass production as layers of devices that could look like thin panels, similar to solar panels or the flat panel displays we see everywhere, manufactured at low cost. Multiple energy storage panels would be stacked together inside a car battery system or solar panel. In the longer run, they foresee the same nanotechnologies providing new energy capture technology (solar, thermoelectric) that could be fully integrated with storage devices in manufacturing.
This advance follows soon after another accomplishment, the dramatic improvement in performance (energy and power) of electrochemical capacitors (ECC's), thus 'supercapacitors,' by Lee's research group, published recently in the Journal of the American Chemical Society. (Figure 1). Efforts are under way to achieve comparable advances in energy density of lithium (Li) ion batteries but with much higher power density.
"The University of Maryland's successes are built upon the convergence and collaboration of experts from a wide range of nanoscale science and technology areas with researchers already in the center of energy research," Rubloff said.
The Research Team
Gary Rubloff is Minta Martin Professor of Engineering in the materials science and engineering department and the Institute for Systems Research at the University of Maryland's A. James Clark School of Engineering. Sang Bok Lee is associate professor in the Department of Chemistry and Biochemistry at the College of Chemical and Life Sciences and WCU (World Class University Program) professor at KAIST (Korea Advanced Institute of Science and Technology) in Korea. Lee and Rubloff are part of a larger team developing nanotechnology solutions for energy capture, generation, and storage at Maryland. Their collaborators on electrical energy storage include Maryland professors Michael Fuhrer (physics), associate director of the Maryland Nanocenter Reza Ghodssi (electrical and computer engineering), John Cumings (materials science engineering), Ray Adomaitis (chemical and biomolecular engineering), Oded Rabin (materials science and engineering), Janice Reutt-Robey (chemistry), Robert Walker (chemistry), Chunsheng Wang (chemical and biomolecular engineering), Yu-Huang Wang (chemistry) and Ellen Williams (physics), director of the Materials Research Science and Engineering Center at the University of Maryland.
Why are nanorods so small?
A new study answers a key question at the very heart of nanotechnology: Why are nanorods so small?
Researchers at Rensselaer Polytechnic Institute have discovered the origins of nanorod diameter, demonstrating that the competition and collaboration among various mechanisms of atomic transport hold the key to nanorod size. The researchers say it is the first study to identify the fundamental reasons why nearly all nanorods have a diameter on the order of 100 nanometers.
“Scientists have been fabricating nanorods for decades, but no one has ever answered the question, ‘Why is that possible?’” said Hanchen Huang, professor in Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, who led the study. “We have used computer modeling to identify, for the first time, the fundamental reasons behind nanorod diameter. With this new understanding, we should be able to better control nanorods, and therefore design better devices.”
Results of the study, titled “A characteristic length scale of nanorods diameter during growth,” were recently published in the journal Physical Review Letters.
When fabricating nanorods, atoms are released at an oblique angle onto a surface, and the atoms accumulate and grow into nanorods about 100 nanometers in diameter. A nanometer is one billionth of a meter in length.
The accumulating atoms form small layers. After being deposited onto a layer, it takes varying amounts of energy for atoms to travel or “step” downward to a lower layer, depending on the step height. In a previous study, Huang and colleagues calculated and identified these precise energy requirements. As a result, the researchers discovered the fundamental reason nanorods grow tall: as atoms are unable to step down to the next lowest layer, they begin to stack up and grow higher.
It is the cooperation and competition of atoms in this process of multi-layer diffusion that accounts for the fundamental diameter of nanorods, Huang shows in the new study. The rate at which atoms are being deposited onto the surface, as well as the temperature of the surface, also factor into the equation.
“Surface steps are effective in slowing down the mass transport of surface atoms, and aggregated surface steps are even more effective,” Huang said. “This extra effectiveness makes the diameter of nanorods around 100 nanometers; without it the diameter would go up to 10 microns.”
Beyond advancing scientific theory, Huang said the discovery could have implications for developing photonic materials and fuel cell catalysts.
Huang co-authored the paper with Rensselaer Research Scientist Longguang Zhou.
Funding for this research was provided by the U.S. Department of Energy Office of Basic Energy Science.
A new study answers a key question at the very heart of nanotechnology: Why are nanorods so small?
Researchers at Rensselaer Polytechnic Institute have discovered the origins of nanorod diameter, demonstrating that the competition and collaboration among various mechanisms of atomic transport hold the key to nanorod size. The researchers say it is the first study to identify the fundamental reasons why nearly all nanorods have a diameter on the order of 100 nanometers.
“Scientists have been fabricating nanorods for decades, but no one has ever answered the question, ‘Why is that possible?’” said Hanchen Huang, professor in Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, who led the study. “We have used computer modeling to identify, for the first time, the fundamental reasons behind nanorod diameter. With this new understanding, we should be able to better control nanorods, and therefore design better devices.”
Results of the study, titled “A characteristic length scale of nanorods diameter during growth,” were recently published in the journal Physical Review Letters.
When fabricating nanorods, atoms are released at an oblique angle onto a surface, and the atoms accumulate and grow into nanorods about 100 nanometers in diameter. A nanometer is one billionth of a meter in length.
The accumulating atoms form small layers. After being deposited onto a layer, it takes varying amounts of energy for atoms to travel or “step” downward to a lower layer, depending on the step height. In a previous study, Huang and colleagues calculated and identified these precise energy requirements. As a result, the researchers discovered the fundamental reason nanorods grow tall: as atoms are unable to step down to the next lowest layer, they begin to stack up and grow higher.
It is the cooperation and competition of atoms in this process of multi-layer diffusion that accounts for the fundamental diameter of nanorods, Huang shows in the new study. The rate at which atoms are being deposited onto the surface, as well as the temperature of the surface, also factor into the equation.
“Surface steps are effective in slowing down the mass transport of surface atoms, and aggregated surface steps are even more effective,” Huang said. “This extra effectiveness makes the diameter of nanorods around 100 nanometers; without it the diameter would go up to 10 microns.”
Beyond advancing scientific theory, Huang said the discovery could have implications for developing photonic materials and fuel cell catalysts.
Huang co-authored the paper with Rensselaer Research Scientist Longguang Zhou.
Funding for this research was provided by the U.S. Department of Energy Office of Basic Energy Science.
Monday, January 28, 2008
An amicable separation
Graphene — a carbon-based nanomaterial known for its unique electronic, thermal and mechanical properties — can form stable dispersions in water without the need for additional chemical stabilizers. The research has practical implications for the development of coatings to reduce static build-up on materials.
Graphene is the name given to the individual sheets of carbon, just one atom thick, that stack together to form graphite. Keeping graphene sheets separate from one another is a difficult task because they tend to stick together, forming larger structures that are not particularly useful. Now, however, using a sequence of chemical reactions, a team led by Gordon Wallace and Dan Li have shown how aqueous dispersions of well-separated graphene sheets can be made from graphite — an abundant and inexpensive starting material.
Rather than relying on either polymer or surfactant stabilizers, their approach maximizes the electrostatic charge on the graphene sheets, ensuring that they repel one another instead of clumping together. This low-cost approach offers the potential for large-scale production of stable graphene colloids that can be processed using well-established solution-based techniques — such as filtration or spraying — to make conductive films. In addition to antistatic coatings, these materials are expected to have applications in flexible transparent electronics, high-performance composites and nanomedicine.
Author contact:
Gordon Wallace (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3127; E-mail: gwallace@uow.edu.au
Dan Li (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3319; E-mail: danli@uow.edu.au
Graphene — a carbon-based nanomaterial known for its unique electronic, thermal and mechanical properties — can form stable dispersions in water without the need for additional chemical stabilizers. The research has practical implications for the development of coatings to reduce static build-up on materials.
Graphene is the name given to the individual sheets of carbon, just one atom thick, that stack together to form graphite. Keeping graphene sheets separate from one another is a difficult task because they tend to stick together, forming larger structures that are not particularly useful. Now, however, using a sequence of chemical reactions, a team led by Gordon Wallace and Dan Li have shown how aqueous dispersions of well-separated graphene sheets can be made from graphite — an abundant and inexpensive starting material.
Rather than relying on either polymer or surfactant stabilizers, their approach maximizes the electrostatic charge on the graphene sheets, ensuring that they repel one another instead of clumping together. This low-cost approach offers the potential for large-scale production of stable graphene colloids that can be processed using well-established solution-based techniques — such as filtration or spraying — to make conductive films. In addition to antistatic coatings, these materials are expected to have applications in flexible transparent electronics, high-performance composites and nanomedicine.
Author contact:
Gordon Wallace (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3127; E-mail: gwallace@uow.edu.au
Dan Li (University of Wollongong, New South Wales, Australia)
Tel: +61 2 4221 3319; E-mail: danli@uow.edu.au
Thursday, December 13, 2007
Nanoscale Details of Photolithography Process Revealed
Description
Scientists at the National Institute of Standards and Technology (NIST) have made the first direct measurements of the infinitesimal expansion and collapse of thin polymer films used in the manufacture of advanced semiconductor devices. It’s a matter of only a couple of nanometers, but it can be enough to affect the performance of next-generation chip manufacturing.
Scientists at the National Institute of Standards and Technology (NIST) have made the first direct measurements of the infinitesimal expansion and collapse of thin polymer films used in the manufacture of advanced semiconductor devices. It’s a matter of only a couple of nanometers, but it can be enough to affect the performance of next-generation chip manufacturing. The NIST measurements, detailed in a new paper,* offer a new insight into the complex chemistry that enables the mass production of powerful new integrated circuits.
The smallest critical features in memory or processor chips include transistor “gates.” In today’s most advanced chips, gate length is about 45 nanometers, and the industry is aiming for 32-nanometer gates. To build the nearly one billion transistors in modern microprocessors, manufacturers use photolithography, the high-tech, nanoscale version of printing technology. The semiconductor wafer is coated with a thin film of photoresist, a polymer-based formulation, and exposed with a desired pattern using masks and short wavelength light (193 nm). The light changes the solubility of the exposed portions of the resist, and a developer fluid is used to wash the resist away, leaving the pattern which is used for further processing.
Exactly what happens at the interface between the exposed and unexposed photoresist has become an important issue for the design of 32-nanometer processes. Most of the exposed areas of the photoresist swell slightly and dissolve away when washed with the developer. However this swelling can induce the polymer formulation to separate (like oil and water) and alter the unexposed portions of the resist at the edges of the pattern, roughening the edge. For a 32-nanometer feature, manufacturers want to hold this roughness to at most about two or three nanometers.
Industry models of the process have assumed a fairly simple relationship in which edge roughness in the exposed “latent” image in the photoresist transfers directly to the developed pattern, but the NIST measurements reveal a much more complicated process. By substituting deuterium-based heavy water in the chemistry, the NIST team was able to use neutrons to observe the entire process at a nanometer scale. They found that at the edges of exposed areas the photoresist components interact to allow the developer to penetrate several nanometers into the unexposed resist. This interface region swells up and remains swollen during the rinsing process, collapsing when the surface is dried. The magnitude of the swelling is significantly larger than the molecules in the resist, and the end effect can limit the ability of the photoresist to achieve the needed edge resolution. On the plus side, say the researchers, their measurements give new insight into how the resist chemistry could be modified to control the swelling to optimal levels.
The research, funded by SEMATECH, is part of a NIST-industry effort to better understand the complex chemistry of photoresists in order to meet the needs of next-generation photolithography. (Newswise)
Description
Scientists at the National Institute of Standards and Technology (NIST) have made the first direct measurements of the infinitesimal expansion and collapse of thin polymer films used in the manufacture of advanced semiconductor devices. It’s a matter of only a couple of nanometers, but it can be enough to affect the performance of next-generation chip manufacturing.
Scientists at the National Institute of Standards and Technology (NIST) have made the first direct measurements of the infinitesimal expansion and collapse of thin polymer films used in the manufacture of advanced semiconductor devices. It’s a matter of only a couple of nanometers, but it can be enough to affect the performance of next-generation chip manufacturing. The NIST measurements, detailed in a new paper,* offer a new insight into the complex chemistry that enables the mass production of powerful new integrated circuits.
The smallest critical features in memory or processor chips include transistor “gates.” In today’s most advanced chips, gate length is about 45 nanometers, and the industry is aiming for 32-nanometer gates. To build the nearly one billion transistors in modern microprocessors, manufacturers use photolithography, the high-tech, nanoscale version of printing technology. The semiconductor wafer is coated with a thin film of photoresist, a polymer-based formulation, and exposed with a desired pattern using masks and short wavelength light (193 nm). The light changes the solubility of the exposed portions of the resist, and a developer fluid is used to wash the resist away, leaving the pattern which is used for further processing.
Exactly what happens at the interface between the exposed and unexposed photoresist has become an important issue for the design of 32-nanometer processes. Most of the exposed areas of the photoresist swell slightly and dissolve away when washed with the developer. However this swelling can induce the polymer formulation to separate (like oil and water) and alter the unexposed portions of the resist at the edges of the pattern, roughening the edge. For a 32-nanometer feature, manufacturers want to hold this roughness to at most about two or three nanometers.
Industry models of the process have assumed a fairly simple relationship in which edge roughness in the exposed “latent” image in the photoresist transfers directly to the developed pattern, but the NIST measurements reveal a much more complicated process. By substituting deuterium-based heavy water in the chemistry, the NIST team was able to use neutrons to observe the entire process at a nanometer scale. They found that at the edges of exposed areas the photoresist components interact to allow the developer to penetrate several nanometers into the unexposed resist. This interface region swells up and remains swollen during the rinsing process, collapsing when the surface is dried. The magnitude of the swelling is significantly larger than the molecules in the resist, and the end effect can limit the ability of the photoresist to achieve the needed edge resolution. On the plus side, say the researchers, their measurements give new insight into how the resist chemistry could be modified to control the swelling to optimal levels.
The research, funded by SEMATECH, is part of a NIST-industry effort to better understand the complex chemistry of photoresists in order to meet the needs of next-generation photolithography. (Newswise)
Saturday, October 13, 2007
World’s fastest supercomputer
RIKEN has taken on the challenge of developing the world’s fastest and most efficient supercomputer.
The computer is to boast a performance of 10 petaflops (that is, 1016 floating-point operations per second) in a general-purpose, compound configuration. RIKEN is to jointly develop the supercomputer with three major manufacturers, Fujitsu Corp., NEC Corp., and Hitachi Ltd, and if all goes according to plan, the new machine will be in operation by 2012.
The supercomputer will be a compound general-purpose configuration, and the project will incorporate the integrated development of both supercomputer and software. The system will feature both a scalar and a vector section, and it will incorporate cutting-edge technology, including 45 nm semiconductor processes and optical interconnection, to achieve compact size and relatively low electric-power consumption for a computer of this capability.
RIKEN will act as project headquarters for the academic–industrial collaboration. When complete, the supercomputer facility will be opened up for use by academic, industrial, and governmental bodies for everything from basic research to commercial applications. Its general-purpose nature will allow it to be used in a wide range of fields of scientific research, from life sciences to nanotechnology.
The project was instigated on orders from the Ministry of Education, Culture, Sports, Science and Technology, to develop the “world’s leading general-purpose supercomputer and the software to use it”. The Ministry also called for the establishment of the world’s most advanced supercomputing Center of Excellence, with the new supercomputer at its center. The Next-Generation Supercomputer R&D Center was established by RIKEN in January 2006.
RIKEN has taken on the challenge of developing the world’s fastest and most efficient supercomputer.
The computer is to boast a performance of 10 petaflops (that is, 1016 floating-point operations per second) in a general-purpose, compound configuration. RIKEN is to jointly develop the supercomputer with three major manufacturers, Fujitsu Corp., NEC Corp., and Hitachi Ltd, and if all goes according to plan, the new machine will be in operation by 2012.
The supercomputer will be a compound general-purpose configuration, and the project will incorporate the integrated development of both supercomputer and software. The system will feature both a scalar and a vector section, and it will incorporate cutting-edge technology, including 45 nm semiconductor processes and optical interconnection, to achieve compact size and relatively low electric-power consumption for a computer of this capability.
RIKEN will act as project headquarters for the academic–industrial collaboration. When complete, the supercomputer facility will be opened up for use by academic, industrial, and governmental bodies for everything from basic research to commercial applications. Its general-purpose nature will allow it to be used in a wide range of fields of scientific research, from life sciences to nanotechnology.
The project was instigated on orders from the Ministry of Education, Culture, Sports, Science and Technology, to develop the “world’s leading general-purpose supercomputer and the software to use it”. The Ministry also called for the establishment of the world’s most advanced supercomputing Center of Excellence, with the new supercomputer at its center. The Next-Generation Supercomputer R&D Center was established by RIKEN in January 2006.
Monday, October 01, 2007
New type of Bismuth oxide nanoparticles
UPM researchers have developed BiOX, a new type of bismuth oxide nanoparticle, which is cheap and ecologically friendly to produce. Bismuth oxide is important in everyday life its non-toxic properties. It can be used as a substitute for lead, eradicating peptic ulcer bacteria, in cosmetics and in solid oxide fuel cell
BiOX: a New Material for Industry
Irmawati Ramli, Nor Hidayaty Kamarulzaman, Norfarizan Ngasriah Mhamat Nasudin, Taufiq-Yap Yun Hin, and Abdul Halim Abdullah
Bismuth oxide is becoming so important in everyday life for its non-toxic and non-carcinogenic status. Demand is rising to use the material as a substitute for lead particularly in copper alloys for plumbing fittings for water drinking system. Suggestions have also been made for including the material in tableware glazing, glasses and crystal ware.
In pharmaceutical industries, the material is proven to be the most effective ingredient eradicating bacteria responsible for inflicting peptic ulcers. The material combined with chloride gives a special pearlescent, inimitable deep luster to lipstick, nail polish, eye shadows and facial powders in addition to its lubricating qualities for smoother, silkier skin comfort.
Other technological applications of bismuth oxide are in the field of advanced ceramics, rare earth chemicals, thermal spray powders, solid oxide fuel cell (SOFC) materials, catalysts, nano-magnetics, electroplating and biotechnology.
BiOX is a new type of bismuth oxide nanoparticle with distinctive bright orange colour. Its chemical symbol is Bi2O3 and its molecular weight is 466. The material particle size is 37nm with its corresponding specific surface area of 8.9m2g-1.
The oxides are of tetragonal-Bi2O3 which through controlled synthesis procedure produce materials resemble into rosette morphology (see attachment for images). The preparation method opted was rather simple and distinguished by the monophase composition of the product, ecological safety and simple operation, therefore promising low operating cost.
contact-
Dr.Irmawati binti Ramli
Address:Department of Chemistry
Faculty of Science
Universiti Putra Malaysia
43400 UPM Serdang
Selangor Darul Ehsan
MALAYSIA
Telephone:+ 603 8946 6786
Facsimile:+ 603 8943 5380
Monday, September 24, 2007
Catching bird flu in a droplet
Detecting bird flu may soon get a whole lot easier.Juergen Pipper and colleagues describe a cheap, fast and effective droplet-based system for detecting the H5N1 virus directly from a throat swab sample in less than 30 minutes. The method could also be adapted to other viruses such as SARS, AIDS and hepatitis B.
In the event of a flu epidemic, its rapid containment would depend on the prompt identification of the first cases. But as routine surveillance may be problematic in countries with limited public health resources, low-cost, easy-to-use detection assays would be are advantageous.
The new system uses droplets that contain particles to automatically isolate, purify and concentrate viral RNA. The method is as sensitive as other available tests, but over one hundred times faster and even cheaper. In addition, it may be applicable not only to the flu virus, but could be adapted to other infectious agents, and to other bodily fluids like blood, urine or saliva.
Author contact:
Juergen Pipper (Institute of Bioengineering and Nanotechnology, Singapore)
Tel: +65 6824 7157; E-mail: jpipper@ibn.a-star.edu.sg
Detecting bird flu may soon get a whole lot easier.Juergen Pipper and colleagues describe a cheap, fast and effective droplet-based system for detecting the H5N1 virus directly from a throat swab sample in less than 30 minutes. The method could also be adapted to other viruses such as SARS, AIDS and hepatitis B.
In the event of a flu epidemic, its rapid containment would depend on the prompt identification of the first cases. But as routine surveillance may be problematic in countries with limited public health resources, low-cost, easy-to-use detection assays would be are advantageous.
The new system uses droplets that contain particles to automatically isolate, purify and concentrate viral RNA. The method is as sensitive as other available tests, but over one hundred times faster and even cheaper. In addition, it may be applicable not only to the flu virus, but could be adapted to other infectious agents, and to other bodily fluids like blood, urine or saliva.
Author contact:
Juergen Pipper (Institute of Bioengineering and Nanotechnology, Singapore)
Tel: +65 6824 7157; E-mail: jpipper@ibn.a-star.edu.sg
In charge of biosensing
A scanning probe microscope capable of detecting changes in the electrical charge on a surface. This technique offers a rapid and sensitive way to sense biological targets, such as DNA and proteins.
Kelvin probe force microscopy (KPFM) is named after Lord Kelvin who investigated how charge is generated when two different materials are brought into close contact. Although KPFM is an established method that has been used to detect biomolecules in microarrays, Angela Belcher and Asher Sinensky have now applied it to measure binding events at the nanoscale. By considering much smaller feature sizes than previously studied, this development has increased both the speed and sensitivity of the technique.
The authors patterned single strands of DNA, which are negatively charged, onto gold substrates and measured their KPFM response. When complementary ‘target’ DNA strands were captured on the surface, the charge density in a given area was doubled and easily detected with KPFM. In this way, Sinensky and Belcher demonstrate the selective sensing of DNA sequences taken from the genes of anthrax and malaria.
Author contact:
Angela Belcher (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 617 252 1163; E-mail: belcher@mit.edu
Albena Ivanisevic (Purdue University, West Lafayette, IN, USA)
Tel: +1 765 496 3676; E-mail: albena@purdue.edu N&V author
A scanning probe microscope capable of detecting changes in the electrical charge on a surface. This technique offers a rapid and sensitive way to sense biological targets, such as DNA and proteins.
Kelvin probe force microscopy (KPFM) is named after Lord Kelvin who investigated how charge is generated when two different materials are brought into close contact. Although KPFM is an established method that has been used to detect biomolecules in microarrays, Angela Belcher and Asher Sinensky have now applied it to measure binding events at the nanoscale. By considering much smaller feature sizes than previously studied, this development has increased both the speed and sensitivity of the technique.
The authors patterned single strands of DNA, which are negatively charged, onto gold substrates and measured their KPFM response. When complementary ‘target’ DNA strands were captured on the surface, the charge density in a given area was doubled and easily detected with KPFM. In this way, Sinensky and Belcher demonstrate the selective sensing of DNA sequences taken from the genes of anthrax and malaria.
Author contact:
Angela Belcher (Massachusetts Institute of Technology, Cambridge, MA, USA)
Tel: +1 617 252 1163; E-mail: belcher@mit.edu
Albena Ivanisevic (Purdue University, West Lafayette, IN, USA)
Tel: +1 765 496 3676; E-mail: albena@purdue.edu N&V author
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